KR101401136B1 - Energy-saving low-cost system and process for producing melamine by means of gas quenching - Google Patents

Abstract

The present invention relates to a melamine production system and process thereof in a gaseous state rapid cooling method, comprising an element cleaning tower in which a fluidized bed reactor, a hot gas cooler, a hot gas filter, a crystallizer, and a melamine collector connected in series to the element cleaning tower are connected in series; Further comprising a gas-liquid separator connected to the fluidized-bed reactor and connected to the carrier gas compressor, the gas-liquid separator being connected to the element cleaning tower, the crystallizer, and the carrier gas compressor. In the melamine production system, a cold air blower is provided between the gas-liquid separator and the crystallizer. The production system according to the present invention has advantages such as high production efficiency, stable operation, low energy consumption, low investment cost, and high exhaust gas economical value.

Description

TECHNICAL FIELD [0001] The present invention relates to a melamine production system and an energy-saving melamine production system using the gas state rapid cooling method,

The present invention relates to the field of melamine production, and more particularly, to an energy and cost-saving melamine production system and a process thereof by a gas-state rapid cooling method.

The chemical formula of melamine is [(NH ₂ ) ₃ C ₃ N ₃ ], which is an organic chemical raw material widely used. It is mainly used for the synthesis of melamine-formaldehyde resin, for living bowl, for interior panel, for fiber finishing, etc. It is also used as paper processing agent in combination with ether. It can also be used as an environmentally friendly high-performance paint cross-linking agent and flame retardant. In the early technology, melamine was produced by the dicyandiamide method. Specifically, first, calcium cyanamide (CaCN ₂ ) was prepared with calcium carbonate (CaC ₂ ), calcium of cyanamide was converted into a dicarboxylic acid It produces dicyandiamide and reheat it again to produce melamine. However, the process for producing melamine by the dicyandiamine process is not economical because the dicyandiamide process has a high cost of calcium carbide.

In order to solve the above problems, the cyano guanidine process has been replaced by the urea process since the 70s of the 20th century, and the urea process uses the urea as a raw material and reacts at a constant temperature, constant pressure or catalytic action as follows.

_{6 (NH 2) 2 CO →} (NH 2) 3 C 3 N 3 + 6NH 3 + 3CO 2

The synthesis process is generally performed under high pressure liquid state rapid cooling (7 to 10 MPa, 370 to 450 ° C), low pressure liquid state rapid cooling method (0.6 to 1 MPa, 380 to 440 ° C) and low pressure gas state rapid cooling method MPa, 390 ° C). The above-mentioned low-pressure gas-state rapid cooling process is advantageous in that the process is simple, the process is simple, the corrosion of the medium is less, the investment cost is reduced, and the construction period is short compared with the high pressure liquid state rapid cooling process and the low pressure liquid state rapid cooling process . Therefore, it is applied with a lot of attention. Low-pressure gaseous rapid cooling has developed rapidly in recent decades, accounting for 55% of the world's total melamine production.

The system of the low pressure gaseous rapid cooling process is as shown in Fig. In the prior art, the low-pressure gaseous rapid cooling process is disclosed in U.S. Patent No. 4,451,271 and Chinese Patent Nos. CN1188761A and CN1493565A. Specifically, it is as follows.

(a) The pressure of the industrial gas discharged from the carrier gas compressor is 0.1 to 0.2 MPa, the temperature of the industrial gas is raised to 360 to 400 ° C with the high temperature molten salt through the carrier gas preheater, and the heated industrial gas is introduced into the fluidized bed reactor A carrier gas preheating step of flowing into the carrier gas;
(b) The element in the molten state at 140 ° C flows into the fluidized bed reactor through the pump, the pressure at the upper part of the reactor is controlled to 0.05 to 0.1 MPa, the temperature is controlled to 390 to 400 ° C, and 85 to 90wt% The melamine is produced by the chemical reaction, and ammonia and CO ₂ (that is, the reaction product and exhaust gas) are produced according to the reaction formula, and the produced melamine is dissolved in the carrier gas and the exhaust gas in the gaseous state. Among them, the catalyst may be porous aluminum oxide, silicon oxide, titanium oxide or aluminum silicate colloid, and the heat of reaction is a chemical reaction step provided by the hot molten salt in the heating tube;
(c) The carrier gas and the exhaust gas in which melamine is dissolved are discharged from the upper part of the fluidized bed, introduced into the hot gas cooler pipe, cooled to 310 to 320 ° C through a low temperature organic heat medium installed outside the pipe, Etc.) is determined and precipitated in an air stream to cool the reaction product gas;

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(d) The gas discharged from the hot gas cooler continuously flows into the hot gas filter cell side, and the gas is introduced into the filtration pipe under the differential pressure action, and the high boiling point byproduct and the catalyst fine particles are blocked by the filtration, thereby purifying the gas . The filter cake attached to the outside of the filter paper is detached through the air, falls to the bottom of the filter, and is periodically discharged to the outside. A constant temperature filtering step of heating and heating the filter to prevent the gas from being cooled from the filter and precipitating melamine;

Since hot gas cooling and filtration is easy to damage piping and equipment and can block piping and equipment, two equipment are installed and one is operated and one is used for spare. This is one of the technical problems of the low-pressure gaseous rapid cooling process and difficulties to solve.
(e) the heat of about 320 ° C discharged from the filter is mixed with the cold air of about 140 ° C emitted from the element cleaning tower, and the temperature is further lowered to 180 to 220 ° C to rapidly cool the crystal in which the melamine crystals precipitate in the gaseous state ;
(f) a gas-solid cyclone separation step in which the melamine crystalline powder is introduced into a melamine collector through an air stream to separate the gas-solid, the separated melamine is extruded from a lower dumping device and transported to a product packing machine;
(g) an industrial gas elevating step in which ammonia, CO ₂ , melamine fine particles and a small amount of unreacted material are contained in the industrial gas from which the melamine powder is separated, and is introduced into the element cleaning tower after being pressurized through a cold air blower;
(h) The industrial gas discharged from the cold air blower is mixed with the low-temperature melting element discharged from the urea pump and then flows to the lower part, and the gas is cleaned and cooled by the element, and the melamine fine particles and the non- Lt; RTI ID = 0.0 > 140 C. < / RTI > The element has a temperature of 136 to 140 캜 after the heat absorption, and again the element is cooled to 127 to 130 캜 through a cooler outside the tower;
(i) The gas-liquid mixture discharged from the element cleaning tower separates the element and the industrial gas through a specially designed defroster, and the separated element flows into the tower and circulates (the gas-liquid separator in the element- State rapid cooling process, which is a difficult task to solve) gas-liquid separation step;
(j) The industrial gas separated through the gas-liquid separator is divided into a crystal cooling gas, a reactor carrier gas and a reaction by-product (exhaust gas). The crystal cooler circulates from the lower part of the crystallizer to the crystallizer and serves to lower the temperature of the reaction product gas. The emulsified carrier gas is used as a catalyst for raising the temperature of the emulsified carrier gas through the carrier gas compressor, raising the temperature by the carrier gas preheater, and circulating it to the reactor to emulsify the carrier gas. The exhaust gas (half of each of NH ₃ and CO ₂ mass) is transferred to the exhaust gas treatment unit, the exhaust gas transport volume is automatically controlled through the pressure of the industrial gas system, and the industrial gas system pressure is generally between 0.01 and 0.05 MPa A feed gas distribution and circulation step to be controlled; .
However, the conventional low-pressure gas-phase rapid cooling process has the following problems.

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1. The production efficiency of the unit volume device is low. In the conventional process using the low-pressure gaseous rapid cooling method, the production efficiency of the unit volume device is low because the pressure inside the melamine reactor is comparatively low, the reactant branching pressure is relatively low, and the chemical reaction rate is slow. In order to achieve higher yields, one line requires a larger volume reactor such as a melamine production unit with an annual output of 30 thousand tons, and a fluidized bed reactor and crystallizer with a diameter of 8 meters or more is required. However, it is not only difficult to design and manufacture the melamine equipment, but also the investment cost. Therefore, it is not possible to further increase the production of one line during the process by the low-pressure gas-phase rapid cooling method.
2. The power consumption of the product is high. The low-pressure gaseous quick-cooling method requires a large amount of industrial gas to be circulated in the apparatus, high pressure, high power carrier gas compressor and cold air blower, so the power consumption of this process is high and generally one ton of melamine power is consumed Not less than 1350 kwh.

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3. The cold air blower can not operate stably for long time. The conventional cold air blower of the melamine process by the low-pressure gas-state rapid cooling method is installed in a melamine collector, and the medium is a melamine saturated industrial gas. Also, the gas contains a large amount of melamine dust that has not been captured by the cyclone separator. Because of the strong centrifugal force of the cold air blower and the heat loss of the main body, the melamine tends to adhere to the blower gas flow path and the case, and the thick melamine crystal fouling is formed to affect the blower operation efficiency and stability. , Maintenance is difficult and costs are added.

4. The recovery or use cost of the by-product melamine exhaust gas is high. The exhaust gas of the process by the low-pressure gaseous state rapid cooling method is free from moisture and is used for many purposes. However, since the pressure of the industrial gas system is only 0.01 to 0.05 MPa and the exhaust gas pressure is relatively low, It is possible to recycle, and the turbine compressor or blower needs to be installed, so energy consumption and investment cost are relatively high.

The production efficiency of the unit volume device by the low-pressure gaseous state rapid cooling method in the prior art is low, the power consumption of the product is high, the cold air blower can not stably operate for a long time, and the recovery or utilization cost of the by-product melamine exhaust gas The present invention aims to provide an energy and cost saving melamine production system and process by a gas-phase rapid cooling method which is high in production efficiency and economical.

The technology and the technical solution in the energy and cost-saving melamine production system and process by the gas-phase rapid cooling method of the present invention are as follows.
The melamine production system by the gaseous rapid cooling method comprises an element cleaning tower in which a fluidized bed reactor, a hot gas cooler, a hot gas filter, a crystallizer, and a melamine collector connected in series to the element cleaning tower are connected in series; Further comprising a gas-liquid separator connected to the fluidized bed reactor and connected to the carrier gas compressor, the gas-liquid separator including the element cleaning tower, the crystallizer, and the carrier gas compressor, And a cold air blower is provided between the determiner.
And a cold air blower is provided between the cold air blower and the crystallizer.
The carrier gas compressor is connected to the gas-liquid separator through the cold air blower.
The carrier gas preheater is a tubular heat exchanger.
The hot gas filter is a bag filter.
The waste heat boiler is connected to the hot gas cooler.
And an in-house evaporative heat exchanger is installed in the element cleaning tower.
The gas-liquid separator is a cyclone deproster.
The production process according to the melamine production system,
(a) after the carrier gas is compressed by the carrier gas compressor, the pressure reaches from 0.36 to 2.1 MPa, the temperature is raised again to 380 to 430 ° C through the carrier gas preheater, and then flows into the fluidized bed reactor as an emulsified gas;
(b) The molten element with a temperature of 135 to 155 ° C flows from the element cleaning tower through the pump into the area of the catalyst-enriched phase in the fluidized bed reactor, and at a reaction pressure of 0.3 to 1.9 MPa and a temperature of 375 to 430 ° C, A melamine synthesis step of reacting to produce a reaction product gas containing melamine, ammonia and CO ₂ ;
(c) the reaction product gas is discharged from the upper portion of the fluidized bed reactor and is introduced into the hot gas cooler so that the high boiling point by-products in the gas are sufficiently crystallized in the air stream and precipitated;
(d) the reaction product gas discharged from the hot gas cooler is introduced into a hot gas filter and then filtered to filter out the high boiling point byproduct and the catalyst fine particles, and the temperature in the hot gas filter is lower than the reaction product gas discharged from the hot gas cooler , The temperature difference being not higher than 3 占 폚;
(e) the reaction product gas discharged from the filter is introduced into the crystallizer and mixed with the crystal cooling gas, and the final temperature of the mixed gas is maintained at 210 to 230 DEG C, and the hot gas is rapidly cooled by cold air, A melamine crystal phase rapid cooling step in which melamine crystals are formed and precipitated from the reaction product gas;
(f) a reaction product gas containing melamine crystals flows into the melamine trap to complete gas-solid separation, and the temperature inside the melamine trap is higher than or equal to the temperature of the gas-solid mixture discharged from the melamine crystallizer, A step of collecting melamine crystals not exceeding 3 DEG C;
(g) The reaction product gas from which the melamine crystals are separated flows out of the melamine collector and then flows into the element cleaning tower, mixed with the melting element at 135-155 DEG C and flows downward. The gas is cleaned and cooled by the element, Cooling and purifying the industrial gas in which all of the melamine fine particles and the unreacted materials are introduced into the melting element;
(h) the gas-liquid mixture exiting from the bottom of the element cleaning tower is separated through a gas-liquid separator and then forms an element and an industrial gas, some of which are circulated for cleaning the reaction product gas again, A gas liquid separation step of introducing melamine into the reactor;
(i) the pressure of the industrial gas separated through the gas-liquid separator is 0.15 to 1.8 MPa, a part of the industrial gas is used as a crystal cooling gas and a carrier gas and the remainder is discharged as exhaust gas, And an industrial gas distribution step in which the pressure is increased through the cold air blower and then circulated from the lower portion of the determiner to return to the determiner.
In the step (i), the crystal cooling gas discharged from the cold air blower is cooled again to 135 to 150 ° C by the cooling cooler, and then circulated from the lower part of the crystallizer to return to the crystallizer.
In the step (i), the carrier gas is introduced into the carrier gas compressor after the pressure rises through the cold air blower.
The catalyst is a granular porous aluminum silicate colloid.
In the step (c), the heat released by the reaction product gas in the hot gas cooler is transferred to the waste heat boiler to heat the medium in the hot water boiler, or the reaction product gas of the hot gas cooler The amount of heat released when the temperature is lowered is transferred to the carrier gas preheater to preheat the carrier gas.
The amount of heat released by the reaction product gas in the step (g) is drawn into an in-pipe evaporative heat exchanger in the urea cleansing tower, the saturated water circulates in the heat exchanger, 150 ° C.
In the step (h), the gas-liquid mixture discharged from the lower part of the element cleaning tower is separated through the gas-liquid separator, and then the element and the industrial gas are formed, and the separated element returns to the element cleaning tower.
In the step (i), the crystal cooling gas is circulated from the lower portion of the crystallizer to the crystallizer after the pressure of the crystal cooling gas is raised to 0.18 to 1.85 MPa through the cold air blower.
In the production process of the present invention, melamine is synthesized in step (b). The molten state element of 135 to 155 ° C flows into the fluidized bed reactor through the pump from the element cleaning tower and melts in the reactor at a reaction pressure of 0.3 to 1.9 MPa and a temperature of 375 to 430 ° C., _2, and during the reaction, the partial pressure of the reactant is increased and the chemical reaction rate is greatly increased, so that about 90 to 99 wt% urea causes a chemical reaction that generates melamine. At the same time, corresponding amounts of ammonia and CO ₂ are produced according to the reaction formula, and melamine is dissolved in the carrier gas and the exhaust gas in the gaseous state.
and the reaction product gas is cooled in step (c). The reaction product gas is discharged from the upper portion of the fluidized bed reactor, flows into the hot gas cooler, and the temperature is lowered so that high boiling point by-products in the gas are sufficiently crystallized and precipitated in the air stream. The final temperature at which the reaction product gas introduced into the hot gas cooler is cooled is determined by the partial pressure of the high boiling point byproduct and the melamine, and the partial pressure is 330 to 360 ° C. In order to clean the crystal fouling of melamine and high boiling point byproducts, the hot gas cooler is preferably a tubular heat exchanger, and the industrial gas discharge heat is applied to the generation of high-quality steam by the waste heat boiler or the preheating of the reaction carrier gas in one step. The temperature of the reaction product gas at the outlet of the hot gas cooler is suppressed by adjusting the level of the waste heat boiler or the reaction carrier gas flow rate.
In step (d), the reaction product gas is filtered. The reaction product gas discharged from the hot gas cooler flows into the high temperature gas filter and is filtered to block the high boiling point catalyst and the catalyst fine particles. The temperature in the high temperature gas filter is lower than the temperature of the reaction product gas discharged from the hot gas cooler Higher or equal, but the temperature difference does not exceed 3 ℃. In order to prevent melamine from being crystallized and precipitated in the filtration process, the gas discharge temperature of the high temperature gas filter must be equal to or slightly higher than the gas inlet temperature. The gas is introduced into the filter under the differential pressure action, and the high-boiling by-product and the fine particles of the catalyst are blocked by the filtration, thereby purifying the reaction product gas. The filter cake attached to the outside of the filtration work is peeled off by the backflow gas and falls to the bottom of the filter, and is periodically discharged to the outside. In order to efficiently and easily clean and recycle in the field, the hot gas filter of the present invention is preferably a bag filter. In addition, it is preferable to install two hot gas coolers and two filters, one for operation and the other for site cleaning and spare.
In step (f), the melamine crystals are collected. The reaction product gas containing melamine crystals flows into the melamine trap and separates the gas-solid. It is preferred that the melamine separator use a cyclone separator to lower the operating pressure of the industrial gas and reduce the maintenance cost of the equipment. In order to prevent the undecrystallized melamine gas from being continuously determined in the melamine collector and adhering to the wall, the gas discharge temperature of the melamine collector must be equal to or slightly higher than the gas inlet temperature. Therefore, the melamine collector is heated and maintained at a temperature of 210 to 230 ° C. to complete the gas-solid separation of the industrial gas and the melamine.
In step (g), the industrial gas is cooled and purified. The reaction product gas from which the melamine crystals are separated is discharged from the melamine collector, flows into the element cleaning tower, mixed with the melting element at 135-155 DEG C and flows downward. The gas is cleaned and cooled by the element, and melamine All the fine particles and unreacted materials are introduced into the melting element, and the gas temperature is lowered from 210 to 230 ° C to 155 ° C. The heat released as the industrial gas temperature is lowered is drawn to the evaporative heat exchanger inside the urea cleansing tower, the saturated water circulates in the heat exchanger piping, and heat is finally discharged from the process system as the saturated water evaporates. In order to prevent the element from forming a crystal fouling inside the heat exchange pipe, the saturated water evaporation temperature is preferably 125 to 150 ° C.
Separate the gas-liquid in step (h). The gas-liquid mixture flowing out from the lower part of the element cleaning tower is separated through the gas-liquid separator and forms an element and an industrial gas, and a part of the element is circulated again to be used for cleaning the reaction product gas, And melamine is synthesized. Separate elements are returned to the element cleaning tower, so there is no need to install element storage separately. The gas-liquid separator in the present invention is preferably a cyclone separator, has high efficiency, low energy consumption, and does not require maintenance.
The industrial gas is dispensed in step (i). A part of the industrial gas separated through the gas-liquid separator is used as a crystal cooling gas and a carrier gas, and the remainder is discharged as exhaust gas. The crystal cooling gas is boosted through the cold air blower, and then returned to the crystallizer while circulating from the lower portion of the crystallizer. The gaseous state pressure of the process system in the present invention is automatically controlled by the exhaust gas flow rate of the exhaust system, and the gas pressure of the process system is preferably 0.15 to 1.8 MPa. The exhaust gas of the exhaust system is transferred to the exhaust gas recycling apparatus. The reactor carrier gas flow rate is controlled by adjusting the carrier gas compressor rotation speed and / or the inlet valve opening / closing degree, and the crystallizer cooling flow rate is controlled by adjusting the cold air blower rotation speed and / or the inlet valve opening / closing degree.

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The energy and cost-saving melamine production system and process thereof by the gas-phase rapid cooling method according to the present invention have the following advantages.
(1) The gas-phase rapid cooling melamine production process according to the present invention increases the reaction pressure to 0.3 to 1.9 MPa, correspondingly increases the industrial gas pressure of the system to 0.15 to 1.8 MPa, The equipment was adjusted accordingly and the design was optimized. By increasing the reaction pressure, the partial pressure of the reactants in the fluidized bed reactor is increased, the chemical reaction rate for synthesizing melamine is significantly increased, the unit volume production amount of each processing apparatus is increased, the volume of the apparatus is decreased, Line production is further improved, reducing the hardware investment and labor investment costs of unit melamine products. Compared with the conventional technology of the same kind, the conventional process technology has a maximum annual production of only 30,000 tons of the individual line melamine due to the pressure vessel design, the technology of the manufacturing standard, and the cost limitation. However, through the process technology of the present invention, It can be realized with a production capacity of 120,000 tons, and the hardware investment used for producing one ton of melamine is 54 ~ 72% of the conventional technology. Further, since the pressure of the system is increased and the gas compression ratio of the carrier gas compressor of the fluidized bed reactor and the cold air blower of the melamine crystallizer is lowered, the gas compression work is greatly reduced and a large amount of energy is saved. According to the conventional technology, the power consumption of 1 ton of melamine is 1350 ~ 1560 kwh, but the power consumption of 1 ton of melamine according to the present invention is 400 ~ 1000 kwh, and power consumption is greatly reduced. The system industrial gas pressure is increased from 0.01 to 0.05 MPa to 0.15 to 1.8 MPa, the melamine exhaust gas pressure and the energy constant are correspondingly improved as compared with the conventional process using the low pressure gas state rapid cooling method, The melamine exhaust gas produced by the technique of the present invention has a higher economic value because the exhaust gas treatment procedure is simplified and equipment investment and energy consumption by the exhaust gas treatment can be reduced.

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Since the melamine production process by the gaseous state rapid cooling method according to the present invention improves not only the reaction pressure but also a series of parameters of the process correspondingly, the reaction rate is effectively increased and the by- It is difficult to separate melamine and the like, so that the above process can be operated normally and efficiently.

 (2) In the melamine production process according to the gas-state rapid cooling method according to the present invention, since the system pressure is increased, the cold air blower must be installed between the industrial gas element cleaning and the melamine crystals. By such a design, the gas inlet temperature of the cold air blower is reduced from 135 to 155 ° C. at 180 to 220 ° C., and the gas volume of the air inlet can be reduced, so that the compression work of the cold air can be further reduced, Advantages of; The advantage of lowering the temperature of the industrial gas at the inlet, thereby facilitating the working conditions of the cold air blower and reducing the blower failure; The melamine crystal fouling of the cold air blower in the conventional technology can be removed and the blower and the process device can be stably operated for a long period of time, thereby shortening the maintenance period of the equipment, reducing the cost, and improving the equipment production rate.

(3) In the melamine production process by the gas-phase rapid cooling method according to the present invention, a cool air cooler is installed at the outlet of the cold air blower. It is necessary to correspondingly increase the circulating amount of the crystal cooling gas so that the gaseous melamine in the reaction product gas is determined because the temperature is increased after the cold air is compressed by the cold air blower. To solve this problem, preferably, the evaporative cooler is used to lower the cool air temperature to the blower inlet gas temperature to reduce the cool air circulation flow rate. With this improvement, the cool air circulation system can save 14 ~ 21% of energy compared to the process without cooler cooler.

In order to facilitate understanding of the present invention, the energy and cost-saving melamine production system and the process thereof according to the gas-phase rapid cooling method of the present invention will be described in detail with reference to the accompanying drawings and specific examples.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a melamine production system by a gas-phase rapid cooling method according to the prior art.
2 is a view showing a melamine production system by the gaseous rapid cooling method according to the present invention.
3 is a view showing a variable system of the melamine production system by the gas-phase rapid cooling method according to the present invention.

Example 1:
As shown in FIG. 2, the melamine production system according to the present embodiment includes a fluidized bed reactor, a high temperature gas cooler, a high temperature gas filter, a crystallizer, a melamine collector connected to the element cleaning tower, (In this embodiment, the hot gas cooler is a tubular cooler); And a carrier gas preheater connected to the fluidized bed reactor and connected to the carrier gas compressor.
The melamine production system further comprises a gas-liquid separator connected to the element cleaning tower, wherein the gas-liquid separator is connected to the crystallizer (the gas-liquid separator according to the present embodiment is a silk screen inertia diffuser) The carrier gas compressor is connected to the gas-liquid separator through a cold air blower, and a cold air blower is provided between the gas-liquid separator and the crystallizer.
The production process of the melamine production system by the gas-phase rapid cooling method according to this embodiment comprises:
(a) after the carrier gas is compressed by the carrier gas compressor, the pressure reaches 0.36 MPa, and the temperature of the carrier gas is increased to 380 ° C through the carrier gas preheater to enter the fluidized bed reactor as an emulsified gas;
(b) A molten element with a temperature of 135 ° C flows from the element cleaning tower through the pump into the catalyst-enriched phase region in the fluidized bed reactor and reacts with the urea under conditions of a reaction pressure of 0.3 MPa and a temperature of 375 ° C to form melamine, A melamine synthesis step to produce a reaction product gas containing CO ₂ (in this example, the catalyst is a porous alumina colloid);
(c) the reaction product gas is discharged from an upper portion of the fluidized bed reactor and introduced into the hot gas cooler to cool the reaction product gas to 330 占 폚 so that the high boiling point by-products in the gas are sufficiently crystallized and precipitated in the gas stream;
(d) the reaction product gas discharged from the hot gas cooler is introduced into the hot gas filter and then filtered to filter out the high boiling point by-product and the catalyst microparticles, and the temperature in the hot gas filter is maintained at 330 ° C. step;
(e) the reaction product gas discharged from the filter is introduced into the crystallizer and mixed with the crystal cooling gas, and the final temperature of the mixed gas is controlled to 180 ° C., and the hot gas is rapidly cooled by the cold air, and most of the gaseous melamine A melamine crystal gaseous state rapid cooling step in which the melamine crystal is formed and crystallized from the reaction product gas and precipitated;
(f) a step of collecting melamine crystals in which a reaction product gas containing melamine crystals is introduced into a melamine collector to separate a gas-solid and a temperature inside the melamine collector is maintained at 210 ° C;
(g) The reaction product gas from which the melamine crystals are separated flows out from the melamine collector and then flows into the element washing tower, mixed with the melting element at 135 캜 and flows downward. The gas is cleaned and cooled by the element, Cooling and purifying the industrial gas in which the fine particles and the unreacted materials are all introduced into the melting element;
(h) the gas-liquid mixture exiting from the lower part of the element cleaning tower is separated through the gas-liquid separator and then formed with the element and the industrial gas, the separated element is sent to the element reservoir, A gas liquid separation step of circulating the product gas for cleaning and the remainder entering the reactor to synthesize melamine;
(i) the pressure of the industrial gas separated through the gas-liquid separator is 0.15 MPa, a part of the industrial gas is used as a crystal cooling gas and a carrier gas, and the remainder is discharged as exhaust gas, And an industrial gas distributing step of circulating from the lower part of the crystallizer after the pressure rises to 0.18 MPa through the cold air blower and returning to the crystallizer and the carrier gas being introduced into the carrier gas compressor after the pressure is raised by the cold air blower .
Example 2:
As shown in FIG. 3, the melamine production system according to the present embodiment includes a fluidized bed reactor, a high-temperature gas cooler, a high-temperature gas filter, a crystallizer, and a melamine collector connected to the element cleaning tower, With towers; And a carrier gas preheater (in this embodiment, the carrier gas preheater is a tubular heat exchanger) connected to the fluidized bed reactor and connected to the carrier gas compressor.
The melamine production system may further include a gas-liquid separator connected to the element cleaning tower, wherein the gas-liquid separator is connected to the crystallizer, the carrier gas compressor is connected to the gas-liquid separator, A cold air blower is provided between the liquid separator and the crystallizer, and a saturated water evaporative cooler is further provided between the cold air blower and the crystallizer.
In this embodiment, the hot gas filter is a metal fiber bag filter, and a saturated water evaporating heat exchanger is installed in the element washing tower.
In this embodiment, the gas-liquid separator is a cyclone diffuser.
The production process of the melamine production system by the gas-phase rapid cooling method according to this embodiment comprises:
(a) after the carrier gas is compressed by the carrier gas compressor, the pressure reaches 2.1 MPa, and then the temperature of the carrier gas is increased to 430 ° C. through the carrier gas preheater to enter the fluidized bed reactor as an emulsion gas;
(b) A molten element having a temperature of 155 ° C flows from the element cleaning tower through the pump into the catalyst-concentrated phase region in the fluidized bed reactor, and the urea reacts under the conditions of a reaction pressure of 1.9 MPa and a temperature of 430 ° C to form melamine, A melamine synthesis step to produce a reaction product gas containing CO ₂ (in this example, the catalyst is a porous alumina colloid);
(c) the reaction product gas is discharged from an upper portion of the fluidized bed reactor and is introduced into the hot gas cooler, thereby lowering the temperature to 360 ° C so that the high boiling point by-products in the gas are sufficiently crystallized and precipitated in the gas stream;
(d) The reaction product gas discharged from the high-temperature gas cooler is introduced into the high-temperature gas filter and then filtered to filter the dehydrogenated condensed compound and the like, which are the high-boiling point by-products, and the catalyst microparticles, and the temperature in the high- A reaction producing gas filtering step;
(e) The reaction product gas discharged from the filter is introduced into the crystallizer and mixed with the crystal cooling gas, and the final temperature of the mixed gas is controlled to 230 ° C., and the hot gas is rapidly cooled by the cold air so that most of the gaseous melamine A melamine crystal gaseous state rapid cooling step in which the melamine crystal is formed and crystallized from the reaction product gas and precipitated;
(f) a step of collecting melamine crystals in which a reaction product gas containing melamine crystals flows into a melamine collector to separate a gas-solid, and the temperature inside the melamine collector is maintained at 230 ° C;
(g) The reaction product gas from which the melamine crystals are separated flows out from the melamine collector and then flows into the element washing tower, mixed with the melting element at 155 DEG C and flows downward. The gas is cleaned and cooled by the element, Cooling and purifying the industrial gas in which the fine particles and the unreacted materials are all introduced into the melting element;
(h) the gas-liquid mixture exiting from the bottom of the element cleaning tower is separated through a gas-liquid separator and then forms an element and an industrial gas, the separated element is sent to the element reservoir, A gas liquid separation step of circulating the product gas for cleaning and the remainder entering the reactor to synthesize melamine;

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(i) the pressure of the industrial gas separated through the gas-liquid separator is 1.8 MPa, a part of the industrial gas is used as a crystal cooling gas and a carrier gas, and the remainder is discharged as exhaust gas, And then returning to the crystallizer after circulating from the lower portion of the crystallizer after cooling to 150 ° C by the cooling chiller after the pressure is raised to 1.85 MPa through the cold air blower.
The heat released by the reaction product gas in the step (g) is drawn into the evaporative heat exchanger in the urea cleansing tower, the saturated water circulates in the heat exchanger, and the heat is finally evaporated System, and the evaporation temperature of the saturated water is 135 占 폚.
Example 3:
The melamine production system by the gas-phase rapid cooling method according to the present embodiment is the same as that of the second embodiment.
The production process of the melamine production system by the gas-phase rapid cooling method according to the present embodiment
(a) the carrier gas is compressed by the carrier gas compressor and then the pressure reaches 0.5 MPa, and the reaction product gas and the hot molten salt through the carrier gas preheater are heated to 400 ° C and introduced into the fluidized bed reactor as emulsified gas ;
(b) A molten element with a temperature of 140 ° C flows from the element cleaning tower through the pump into the catalyst-enriched phase region in the fluidized bed reactor and the urea reacts under the conditions of a reaction pressure of 0.4 MPa and a temperature of 380 ° C to form melamine, ammonia, A melamine synthesis step (in this embodiment, the catalyst is a particulate porous aluminum silicate colloid) to produce a reaction product gas containing CO ₂ ;
(c) the reaction product gas is discharged from the upper portion of the fluidized bed reactor and flows into the hot gas cooler to lower the temperature to 340 캜 so that the high boiling point by-products in the gas are sufficiently crystallized and precipitated in the gas stream, A reaction product gas cooling step of transferring the heat released when the temperature is lowered to the carrier gas preheater to preheat the carrier gas;
(d) the reaction product gas discharged from the hot gas cooler is introduced into the hot gas filter and then filtered to filter the high boiling point by-product and the catalyst microparticles, and the temperature in the hot gas filter is maintained at 340 ° C. step;
(e) the reaction product gas discharged from the filter is introduced into the crystallizer and mixed with the crystal cooling gas, and the final temperature of the mixed gas is controlled to 210 DEG C, and the hot gas is rapidly cooled by the cold air so that most of the gaseous melamine A melamine crystal gaseous state rapid cooling step in which the melamine crystal is formed and crystallized from the reaction product gas and precipitated;
(f) a step of collecting melamine crystals in which a reaction product gas containing melamine crystals flows into a melamine collector to separate a gas-solid, and the temperature inside the melamine collector is maintained at 213 ° C;
(g) The reaction product gas from which the melamine crystals are separated flows out from the melamine collector and then flows into the element cleaning tower, mixed with the melting element at 140 캜 and flows downward. The gas is cleaned and cooled by the element, Cooling and purifying the industrial gas in which the fine particles and the unreacted materials are all introduced into the melting element;
(h) the gas-liquid mixture exiting from the bottom of the element cleaning tower is separated through a gas-liquid separator, then forming an element and an industrial gas, the separated element returning to the element scrubbing tower, A gas liquid separation step of circulating the product gas for cleaning and the remainder entering the reactor to synthesize melamine;

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(i) the pressure of the industrial gas separated through the gas-liquid separator is 0.4 MPa, a part of the industrial gas is used as a crystal cooling gas and a carrier gas, and the remainder is discharged as exhaust gas, Cooling the refrigerant to 135 ° C by the evaporative cooling cooler after returning the pressure to 0.43 MPa through a cold air blower, and circulating the refrigerant from the lower part of the crystallizer to return to the crystallizer.
The heat released by the reaction product gas in the step (g) is drawn into the evaporative heat exchanger in the urea cleansing tower, the saturated water circulates in the heat exchanger, and the heat is finally evaporated System, and the evaporation temperature of the saturated water is 150 [deg.] C.

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In the above embodiment, the hot gas filter and the melamine trap are both provided with a heating device to attain the object of keeping warmth. This is a well-known knowledge to those skilled in the art, and a description thereof will be omitted. In addition, in the above embodiment, all of the hot gas filters use a bag filter, and the bag of the bag filter is used in the prior art such as a high temperature resistant glass fiber felt (or cloth) or a corrosion resistant metal fiber felt It is selectable as a filter media to be applied arbitrarily, and the filter may use any fine hole filter according to the prior art.

Comparative Example:
In order to prove that the melamine production system and the process thereof by gas-phase rapid cooling according to the present invention have a remarkable technical effect as compared with the conventional technology, the technical effect of the present invention Will be described in more detail. In the comparative example, a low-pressure gaseous quick cooling method according to the prior art was used, and the system diagram thereof is shown in Fig. Actual measured values and effects in the above Examples and Comparative Examples are shown in the following table.

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As can be seen from the above results, in the process according to the comparative example, the power consumption of 1 ton of the melamine product and the value of the facility investment ratio of 60,000 tons per year are much larger than the corresponding values of the processes described in Examples 1 to 3, The example process can only be implemented through two production lines. Therefore, the production system and the process according to the present invention are superior to the melamine production system and process by the gas state rapid cooling method according to the prior art, and have a high production efficiency, a long operating cycle, a low capital investment cost, And the exhaust gas utilization ratio is high. Therefore, the technical solution according to the present invention has a substantial technical effect as compared with the conventional technical solution.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And modifications are within the scope of the present invention.

Claims (17)

An element cleaning tower in which a fluidized bed reactor, a hot gas cooler, a hot gas filter, a crystallizer, and a melamine collector connected in series to the element cleaning tower are connected in series;
And a carrier gas preheater connected to the fluidized bed reactor and connected to the carrier gas compressor,
Further comprising a gas-liquid separator connected to the element cleaning tower, the crystallizer, and the carrier gas compressor, the melamine producing apparatus comprising:
And a cold air blower is installed between the gas-liquid separator and the crystallizer. The method according to claim 1,
And a cool air cooler is provided between the cold air blower and the crystallizer. 3. The method according to claim 1 or 2,
Wherein the carrier gas compressor is connected to the gas-liquid separator through the cold air blower. 3. The method according to claim 1 or 2,
Wherein the carrier gas preheater is a tubular heat exchanger. 5. The method of claim 4,
Wherein the high temperature gas filter is a bag filter. 6. The method of claim 5,
And a waste heat boiler is connected to the high-temperature gas cooler. The method according to claim 6,
And an evaporator-type heat exchanger is installed in the element cleaning tower. 8. The method of claim 7,
Characterized in that the gas-liquid separator is a cyclone deproster. (a) after the carrier gas is compressed by the carrier gas compressor, the pressure reaches from 0.36 to 2.1 MPa, the temperature is raised again to 380 to 430 ° C through the carrier gas preheater, and then flows into the fluidized bed reactor as an emulsified gas;
(b) The molten element with a temperature of 135 to 155 ° C flows from the element cleaning tower through the pump into the area of the catalyst-enriched phase in the fluidized bed reactor, and at a reaction pressure of 0.3 to 1.9 MPa and a temperature of 375 to 430 ° C, A melamine synthesis step of reacting to produce a reaction product gas containing melamine, ammonia and CO ₂ ;
(c) the reaction product gas is discharged from the upper portion of the fluidized bed reactor and is introduced into the hot gas cooler so that the high boiling point by-products in the gas are sufficiently crystallized in the air stream and precipitated;
(d) the reaction product gas discharged from the hot gas cooler is introduced into a hot gas filter and then filtered to filter out the high boiling point byproduct and the catalyst fine particles, and the temperature in the hot gas filter is lower than the reaction product gas discharged from the hot gas cooler , The temperature difference being not higher than 3 占 폚;
(e) the reaction product gas discharged from the filter is introduced into the crystallizer and mixed with the crystal cooling gas, and the final temperature of the mixed gas is maintained at 210 to 230 DEG C, and the hot gas is rapidly cooled by cold air, A melamine crystal gaseous state rapid cooling step in which a majority of the melamine crystals are formed and precipitated from the reaction product gas;
(f) a reaction product gas containing melamine crystals flows into the melamine trap to complete gas-solid separation, and the temperature inside the melamine trap is higher than or equal to the temperature of the gas-solid mixture discharged from the melamine crystallizer, A step of collecting melamine crystals not exceeding 3 DEG C;
(g) The reaction product gas from which the melamine crystals are separated flows out of the melamine collector and then flows into the element cleaning tower, mixed with the melting element at 135-155 DEG C and flows downward. The gas is cleaned and cooled by the element, Cooling and purifying the industrial gas in which all of the melamine fine particles and the unreacted materials are introduced into the melting element;
(h) the gas-liquid mixture exiting from the bottom of the element cleaning tower is separated through a gas-liquid separator and then forms an element and an industrial gas, some of which are circulated for cleaning the reaction product gas again, A gas liquid separation step of introducing melamine into the reactor;
(i) the pressure of the industrial gas separated through the gas-liquid separator is 0.15 to 1.8 MPa, a part of the industrial gas is used as a crystal cooling gas and a carrier gas and the remainder is discharged as exhaust gas, And an industrial gas distributing step of circulating from the lower part of the crystallizer after the pressure rises through the cold air blower and returning to the crystallizer. (a) after the carrier gas has been compressed by the carrier gas compressor, the pressure reaches from 0.36 to 2.1 MPa, and the temperature is raised again to 380 to 430 ° C through the carrier gas preheater to enter the fluidized bed reactor as a flowing gas;
(b) The molten element with a temperature of 135 to 155 ° C flows from the element cleaning tower through the pump into the area of the catalyst-enriched phase in the fluidized bed reactor, and at a reaction pressure of 0.3 to 1.9 MPa and a temperature of 375 to 430 ° C, A melamine synthesis step of reacting to produce a reaction gas containing melamine, ammonia and CO ₂ ;
(c) the reaction product gas is discharged from the upper portion of the fluidized bed reactor and is introduced into the hot gas cooler so that the high boiling point by-products in the gas are sufficiently crystallized in the air stream and precipitated;
(d) the reaction product gas discharged from the hot gas cooler is introduced into a hot gas filter and then filtered to filter out the high boiling point byproduct and the catalyst fine particles, and the temperature in the hot gas filter is lower than the reaction product gas discharged from the hot gas cooler A reaction product gas filtering step in which the temperature difference is equal to or higher than the temperature of the reaction product gas, but the temperature difference does not exceed 3 deg.
(e) the reaction product gas discharged from the filter is introduced into the crystallizer and mixed with the crystal cooling gas, and the final temperature of the mixed gas is maintained at 210 to 230 DEG C, and the hot gas is rapidly cooled by cold air, A melamine crystal gaseous state rapid cooling step in which a majority of the melamine crystals are formed and precipitated from the reaction product gas;
(f) a reaction product gas containing melamine crystals flows into the melamine trap to complete gas-solid separation, and the temperature inside the melamine trap is higher than or equal to the temperature of the gas-solid mixture discharged from the melamine crystallizer, A step of collecting melamine crystals not exceeding 3 DEG C;
(g) The reaction product gas from which the melamine crystals are separated flows out of the melamine collector and then flows into the element cleaning tower, mixed with the melting element at 135-155 DEG C and flows downward. The gas is cleaned and cooled by the element, Cooling and purifying the industrial gas in which all of the melamine fine particles and the unreacted materials are introduced into the melting element;
(h) the gas-liquid mixture exiting from the bottom of the element scrubbing tower is separated through a gas-liquid separator and then forms an element and an industrial gas, some of which are recycled back to the reaction product gas scrubber, A gas liquid separation step of introducing melamine into the reactor;
(i) the pressure of the industrial gas separated through the gas-liquid separator is 0.15 to 1.8 MPa, a part of the industrial gas is used as a crystal cooling gas and a carrier gas, and the remainder is discharged as exhaust gas, Wherein the gas is circulated from the lower portion of the crystallizer after the pressure rises through the cold air blower and returns to the crystallizer. 11. The method of claim 10,
In the step (i), the crystal cooling gas discharged from the cold air blower is cooled again to 135 to 150 ° C by the cooling cooler, and then circulated from the lower part of the crystallizer to return to the crystallizer. 10. The method of claim 9,
Wherein the carrier gas is introduced into the carrier gas compressor after the pressure of the carrier gas is increased through the cold air blower in the step (i). 10. The method of claim 9,
Wherein the catalyst is a granular porous aluminum silicate colloid. 11. The method of claim 10,
In the step (c), the heat released by the reaction product gas in the hot gas cooler is transferred to the waste heat boiler to heat the medium in the superheat boiler, or the reaction product gas of the hot gas cooler And the heat released during the temperature lowering is transferred to the carrier gas preheater to preheat the carrier gas. 11. The method of claim 10,
The heat released by the reaction product gas in the step (g) is drawn into an in-pipe evaporative heat exchanger inside the element cleaning tower, and the saturated water circulates in the heat exchanger, and the evaporation temperature of the saturated water is 125 ~ Lt; RTI ID = 0.0 > 150 C. < / RTI > 10. The method of claim 9,
In the step (h), the gas-liquid mixture discharged from the lower part of the element cleaning tower is separated through the gas-liquid separator and forms an element and an industrial gas, and some of the separated elements return to the element cleaning tower The characteristic melamine production process. 10. The method of claim 9,
In the step (i), the crystal cooling gas is circulated from the lower portion of the crystallizer to the crystallizer after the pressure of the crystal cooling gas is raised to 0.18 to 1.85 MPa through the cold air blower.

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